Chemokines are chemotactic cytokines that are released by a wide variety of cells to attract leukocytes, as illustrated by macrophages, T cells, B cells, eosinophils, basophils, and neutrophils to and from sites of inflammation or within specific compartments, as illustrated by lymph nodes (reviewed in Schall, Cytokine, 3:165-183 (1991), Schall, et al., Curr. Opin. Immunol., 6:865-873 (1994) and Murphy, Rev. Immun., 12:593-633 (1994)). In addition to stimulating chemotaxis, other changes can be selectively induced by chemokines in responsive cells, including changes in cell shape, transient rises in the concentration of intracellular free calcium ions ([Ca2+]), granule exocytosis, integrin upregulation, formation of bioactive lipids (e.g., leukotrienes), and respiratory burst, associated with leukocyte activation. Thus, the chemokines are early modulators of inflammatory response, effecting inflammatory mediator release, chemotaxis and extravasation to sites of infection or inflammation.
There are four classes of chemokines, CXC (α), CC (β), C (γ), and CX3C (δ), depending on whether the first two cysteines are separated by a single amino acid (C-X-C), are adjacent (C-C), have a missing cysteine pair (C), or are separated by three amino acids (CX3C). The α-chemokines, such as interleukin-8 (IL-8), melanoma growth stimulatory activity protein (MGSA), and stromal cell derived factor 1 (SDF-1) are chemotactic primarily for neutrophils and lymphocytes, whereas β-chemokines, such as RANTES, MIP-1α, MIP-1β, monocyte chemotactic protein-1 (MCP-1), MCP-2, MCP-3, and eotaxin are chemotactic for macrophages, T-cells, eosinophils and basophils (Deng, et al., Nature, 381:661-666 (1996)). The C chemokine lymphotactin shows specificity for lymphocytes (Kelner, et al., Science, 266:1395-1399 (1994)) while the CX3C chemokine fractalkine shows specificity for lymphocytes and monocytes (Bazan, et al., Nature, 385:640-644 (1997)).
Chemokines bind specific cell-surface receptors belonging to the family of G-protein-coupled seven-transmembrane-domain proteins (reviewed in Horuk, Trends Pharm. Sci., 15:159-165 (1994)) termed “chemokine receptors.” On binding their cognate ligands, chemokine receptors transduce an intracellular signal through the associated heterotrimeric G protein, resulting in a rapid increase in intracellular calcium concentration. There are at least twelve human chemokine receptors that bind or respond to β-chemokines with the following characteristic pattern: CCR1 (or “CKR-1” or “CC-CKR-1”) MIP-1α, MIP-1β, MCP-3, RANTES (Ben-Barruch, et al., J. Biol. Chem., 270:22123-22128 (1995); Neote, et al., Cell, 72:415425 (1993)); CCR2A and CCR2B (or “CKR-2A”/“CKR-2A” or “CC-CKR-2A”/“CC-CKR2A”) MCP-1, MCP-2, MCP-3, MCP-4; CCR3 (or “CKR-3” or “CC-CKR-3”) eotaxin, RANTES, MCP; (Ponath, et al., J. Exp. Med., 183:2437-2448 (1996)); CCR4 (or “CKR-4” or “CC-CKR-4”) TARC, MDC (Imai, et al., J. Biol. Chem., 273:1764-1768 (1998)); CCR5 (or “CKR-5” or “CC-CKR-5”) MIP-1α, RANTES, MIP-1β; (Sanson, et al., Biochemistry, 35:3362-3367 (1996)); CCR6MIP-3a (Greaves, et al., J. Exp. Med., 186:837-844 (1997)); CCR7MIP-3β and 6Ckine (Campbell, et al., J. Cell. Biol., 141:1053-1059 (1998)); CCR8 I-309, HHV8 vMIP-I, HHV-8 vMIP-II, MCV vMCC-I (Dairaghi, et al., J. Biol. Chem., 274:21569-21574 (1999)); CCR9 TECK (Zaballos, et al., J. Immunol., 162:5671-5675 (1999)), D6 MIP-1 beta, RANTES, and MCP-3 (Nibbs, et al., J. Biol. Chem., 272:32078-32083 (1997)), and the Duffy blood-group antigen RANTES, MCP-1 (Chaudhun, et al., J. Biol. Chem., 269:7835-7838 (1994)).
Chemokine receptors, such as CCR1, CCR2, CCR3, CCR4, CCR5, CCR6, CCR7, CCR8, CCR9, CXCR1, CXCR2, CXCR3, CXCR4, CXCR5, CX3CR1, and XCR1 have been implicated as being important mediators of inflammatory and immunoregulatory disorders and diseases, including asthma and allergic diseases, as well as autoimmune pathologies such as rheumatoid arthritis and atherosclerosis.
The CCR2 chemokine receptor is expressed primarily in monocytes and activated T lymphocytes, and its functional activity can be measured by cytosolic calcium elevation or chemotaxis. CCR2 exists in two isoforms, CCR2A and CCR2B. These two isoforms are alternatively spliced variants of a single MCP-1 receptor gene and differ only in the carboxyl-terminal tails. The chromosomal location of the CCR2 gene is localized to 3p21. Ligands that have been identified that are selective and of high affinity are the CC chemokines, MCP-1, MCP-2, MCP-3 and MCP-4.
The highly selective expression of CCR2 makes it an ideal target for intervention to interrupt inappropriate monocyte and T cell trafficking. The clinical indications for such intervention are in inflammatory diseases and T-cell mediated autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, asthma, allergy, chronic obstructive pulmonary disease, atherosclerosis, restinosis, type I and type II diabetes, metabolic syndrome and neuropathic pain. Ectopic expression of MCP-1 and CCR2 in certain tumors indicate that selective antagonists of CCR2 will have value in tumor immunotherapy, particularly attenuation of metastasis.
In view of the clinical importance of CCR2, the identification of compounds that modulate CCR2 function represents an attractive avenue into the development of new therapeutic agents. Such compounds are provided herein.